Regarding image display devices in personal computers, mobile telephones and the like, image display devices that would display the display light coming from a display panel as images and would be utilized as mirrors in a situation where there is no display light, by providing a half-mirror film in the inside or outside of the vicinity on the viewer's side of the image display device, have been hitherto developed (for example, Patent Documents 1 to 3).
Meanwhile, in recent years, opportunities for using capacitive touch panels have dramatically increased as a result of wide distribution of mobile electronic devices such as so-called smart phones and tablet terminals.
Such a capacitive touch panel is generally configured to have a position input device comprising an insulator film, a patternized transparent conductive layer and the like provided on a display panel such as a liquid crystal display panel or an organic electroluminescent display panel. Furthermore, there also exist capacitive touch panels having a so-called in-cell type configuration, in which a position input means is incorporated into a display panel.
Furthermore, a capacitive touch panel is incorporated into a housing together with other control instruments on the occasion of constructing an image display device, and a protection plate made of glass or a resin is provided on the viewer's side. At this time, there may be a gap between the protection plate and the capacitive touch panel, or the gap may be filled with an adhesive or a pressure-sensitive adhesive.
Furthermore, in a capacitive touch panel, a very low voltage is applied to a transparent conductive film, charge is accumulated on the surface of the transparent conductive film, and thereby an electric field is formed on the surface. Regarding the surface, when a conductor such as a finger or a touch pen touches on the capacitive touch panel, discharge occurs, and the electric field undergoes a slight change.
Therefore, in a capacitive touch panel, the position of contact by a finger or the like would be specified by detecting such slight change in the electric field.